Figure 4.

Regression coefficient of ecological factors (A,C,E,G) and VIP (B,D,F,H) of volatile oil and non-volatile ether extract contents in Z. armatum and Z. bungeanum (the whiskers represent standard deviation). x1 Elevation, x2 Active accumulated temperature, x3 Sunshine duration, x4 Average annual temperature, x5 Minimum temperature in January, x6 Average temperature in January, x7 Maximum temperature in July, x8 Average temperature in July, x9 Annual precipitation, x10 Relative humidity. VIP scores larger than 1 indicated the most significant ecological factors, and the scores between 1 and 0.5 indicated the significant ecological factors, and the scores lower than 0.5 indicated the unimportant ecological factors.